Drop and insert channel bank with reduced channel units

Abstract

A drop and insert channel bank is provided for receiving data from and inserting data onto a multichannel digital transmission line, such as a microwave radio link, between end terminals. The channel bank has a plurality of single channel units which share common equipment, including a receiver and a transmitter from and to the transmission line and a switching unit therebetween. The switching unit includes user controlled selection circuitry enabling any channel on the line to be dropped to any of the channel units, and enabling any channel to be inserted on the line from any of the channel units. Through-traffic passes through the receiver, switching unit and transmitter of the channel bank in digital form without conversion to and from analog form. Unidirectional and bidirectional modes are disclosed, including various forms of each.

We claim: 
     
       1. A drop and insert channel bank for a digital transmission system carrying a plurality of multiplexed channels on a transmission medium between a pair of terminals, comprising: a receive unit connected to said transmission medium for receiving said channels;   a transmit unit connected to said transmission medium for transmitting said channels;   a data switching unit connected between said receive unit and said transmit unit for selectively dropping any one or more channels through said receive unit and inserting any one or more channels through said transmit unit, including means for passing noninserted channels through said data switching unit solely in digital form, without conversion to and from analog form;   a plurality of channel units each corresponding to an individual channel, connected to and sharing in common, said data switching unit;   said receive unit comprising means demultiplexing data from said transmission medium into a matrix of X channel strobes by Y data buses;   said data switching unit including a receive portion having a channel strobe and data bus selector pair for each of said channel units, said pair delivering a single channel strobe and single data bus to its respective channel unit to uniquely define one of said channels;   said transmit unit comprising means multiplexing Y data buses from said data switching unit for serial transmission over said transmission medium; and   said data switching unit further including a transmit portion having a channel strobe and data bus distributor pair for each of said channel units, said pair selectively distributing data from its respective channel unit into one channel time slot on one of Y data buses to said transmit unit to uniquely define one of said channels into which said last mentioned data is inserted, each channel thereby being selectable to carry data from or to any said channels in said transmission medium through said commonly shared data switching unit, whereby to enable any of said channels on said transmission medium to be dropped or inserted without fully equipping said channel bank with dedicated equipment for every said channel.   
     
     
       2. The invention according to claim 1 wherein said transmit portion of said data switching unit further includes: an insert selector for each of the Y data buses to said transmit unit, each insert selector having a control input from said channel strobe distributors, a first data input from data bus distributors, and a second data input for through-traffic, said insert selector normally choosing said second data input and delivering through-traffic to its respective data bus to said transmit unit, said insert selector choosing said first data input in response to a channel strobe enable signal at said control input for delivering insert data during the strobed channel time slot from said data bus distributors.   
     
     
       3. The invention according to claim 2 wherein said transmit portion of said data switching unit further includes inhibit gates between said insert selectors and transmit unit, and an inhibit controller for controlling said inhibit gates such that a pair of identical said data switching units may be connected in master slave relation to increase the channel unit capacity of said bank. 
     
     
       4. The invention according to claim 2 wherein: said receive unit and said transmit unit are connected to oppositely directed eastbound and westbound portions of said transmission medium, respectively;   said channel bank further includes a westbound receive unit connected between said westbound portion of said transmission medium and said data switching unit such that westbound through-traffic travels through said westbound receive unit then through said data switching unit then through said westbound transmit unit;   said westbound receive unit comprises means demultiplexing data from said transmission medium into a matrix of X channel strobes by Y data buses;   said transmit portion of said data switching unit further includes a set of channel strobe selectors, one for each said channel unit, each selector receiving X channel strobes from said westbound receive unit and selectively delivering a single channel strobe to the respective said channel unit for that selector for strobing data from that channel unit to its respective said data bus distributor, the outputs of said last mentioned channel strobe selectors also being delivered to respective said channel strobe distributors; and   each said insert selector receives a respective one of said last mentioned Y data buses at said second data input.   
     
     
       5. The invention according to claim 2 wherein: said receive unit and said transmit unit are connected to a commonly directed portion of said transmission medium;   through-traffic on said commonly directed portion travels through said receive unit then through said data switching unit then through said transmit unit;   said single channel strobes from said channel strobe selectors in said receive portion of said data switching unit to respective said channel units for dropping data thereto also strobe insert data from said channel units to respective said data bus distributors in said transmit portion of said data switching unit;   the outputs of said channel strobe selectors in said receive portion of said data switching unit are also connected to respective said channel strobe distributors in said transmit portion of said data switching unit; and   said Y data buses from said receive unit are also connected to respective said insert selectors at said second data input for passage to respective said Y data buses to said transmit unit in the absence of a channel strobe enable signal at said control input.   
     
     
       6. A drop and insert channel bank for a digital transmission system carrying a plurality of multiplexed channels on a transmission medium between a pair of terminals, comprising: a receive unit connected to said transmission medium for receiving said channels;   a transmit unit connected to said transmission medium for transmitting said channels;   a data switching unit connected between said receive unit and said transmit unit for selectively dropping any one or more channels through said receive unit and inserting any one or more channels through said transmit unit; and   a plurality of channel units each corresponding to an individual channel connected to and sharing in common said data switching unit, each channel unit selectable to carry data from or to any of said channels in said transmission medium through said commonly shared data switching unit, whereby to enable any of said channels on said transmission medium to be dropped or inserted without fully equipping said channel bank with dedicated equipment for every said channel,   said data switching unit comprising means for generating an inhibit command, and selective output control means for blocking passage of channels to said transmit unit in response to an inhibit command, such that a pair of identical said data switching units may be used in master/slave relation with said inhibit command means of one data switching unit connected to said selective output control means of the other data switching unit, each said data switching unit having its own set of said channels units but sharing the same said transmit unit, whereby to double the channel unit capacity of an existing said channel bank by a simple add-on slave data switching unit without duplicating the entire channel bank.   
     
     
       7. A channel bank for a transmission system carrying a plurality of multiplexed digital channels on a transmission medium between a pair of terminals, comprising: receiver means connected to said transmission medium for receiving said channels and comprising demultiplexer means demultiplexing data from said transmission medium into Y buses of X channels each and outputting Y data buses and X channel strobes;   switching means connected to said receiver means for receiving said Y data buses and said X channel strobes, comprising: N sets of selectors, each set comprising a 1 of X selectors, a 1 of Y selector, and a user controlled channel selector for choosing the 1 of X and 1 of Y selections; and   means connecting said X channel strobes to said 1 of X selector in each of said N sets, and connecting said Y data buses to said 1 of Y selector in each of said N sets, each set outputting a single channel strobe and the data from one of said Y buses as respectively chosen by each said channel selector; and     N channel units each connected to the output of a respective one of said N selector sets.   
     
     
       8. A channel bank for a transmission system carrying a plurality of multiplexed digital channels on a transmission medium between a pair of terminals, comprising: transmit means connected to said transmission medium for inserting one or more channels therein;   switching means connected to said transmit means for selecting one or more channels for insertion;   channel unit means connected to said switching means for sending the channels to be inserted;   receiver means demultiplexing data from said transmission medium into Y buses of X channels each and outputting Y data buses and X channel strobes to said switching means;   said switching means comprising N sets of selectors, each set comprising a 1 of X selector, a 1 to Y distributor, and a user controlled channel selector for choosing the 1 of X selection and the 1 to Y distribution;   said channel unit means comprising N channel units each connected to the input of a respective one of said 1 to Y distributors;   said switching means comprising means connecting said X channel strobes to said 1 of X selectors in each of said N sets, and connecting the outputs of said 1 of X selectors to respective 1 to Y distributors and to respective channel units for strobing data from a channel unit to a 1 to Y distributor, said 1 to Y distributor in each of said N sets outputting data on one of Y buses as chosen by said channel selector for that set;   said switching means comprising Y 1 of 2 selectors and means connecting Y data buses from said demultiplexer means to respective said Y 1 of 2 selectors and connecting said Y data buses and said Y channel strobe buses from each of said N 1 to Y distributors to said 1 of 2 selectors such that each said 1 of 2 selector chooses data from said demultiplexer means in the absence of a channel selection and chooses data from said 1 to Y distributor in response to a channel selection; and   said transmit means comprising multiplexer means multiplexing the data outputs of said Y 1 of 2 selectors.   
     
     
       9. The invention according to claim 8 wherein: said receiver means comprises demultiplexer means demultiplexing data from said transmission medium into Y buses of X channels each and outputting Y data buses and X channel strobes to said switching means;   said switching means comprises N sets of selectors, each set comprising a 1 of X selector, a 1 of Y selector, and a user controlled channel selector for choosing the 1 of X and 1 of Y selections;   said switching means comprises means connecting said X channel strobes to said 1 of X selector in each of said last mentioned N sets, and connecting said Y data buses to said 1 of Y selector in each of said last mentioned N sets, each set outputting a single channel strobe and the data from one of said Y buses as respectively chosen by each said last mentioned channel selector; and   said N channel units are each connected to the output of a respective one of said last mentioned N selector sets.   
     
     
       10. A bidirectional drop and insert channel bank for receiving signals from either or both of a pair of end terminals by dropping one or more channels from a transmission medium therebetween, and for sending signals to either or both of said terminals by inserting one or more channels on said transmission medium, said terminals being assigned designations as a west terminal and an east terminal, and said transmission medium thereby having an eastbound portion and a westbound portion, said channel bank comprising: a pair of receivers comprising an eastbound receiver connected to said eastbound portion of said transmission medium for receiving signals from said west terminal, and a westbound receiver connected to said westbound portion of the transmission medium for receiving signals from the east terminal;   a pair of transmitters comprising a westbound transmitter connected to the westbound portion of the transmission medium for sending signals to the west terminal, and an eastbound transmitter connected to the eastbound portion of the transmission medium for sending signals to the east terminal;   a pair of switching units comprising a west switching unit and an east switching unit;   a pair of groups of one or more channel units comprising a west group of one or more channel units connected to said west switching unit, and an east group of one or more channel units connected to said east switching unit;   means for connecting each of said switching units between one of the receivers and transmitters so that eastbound signal traffic travels through said eastbound receiver then through said east switching unit then through said eastbound transmitter,   eastbound signal traffic is also delivered to said west switching unit for selective delivery of one or more channels to said west channel units,   westbound signal traffic travels through said westbound receiver then through said west switching unit then through said westbound transmitter, and   westbound signal traffic is also delivered to said east switching unit for selected delivery of one or more channels to said east channel units;     each of said receivers comprising means demultiplexing data from said transmission medium into a matrix of X channel strobes by Y data buses;   each of said switching units including a receive portion having a channel strobe and data bus selector pair for each of the associated channel units, said pair delivering a single channel strobe and single data bus to its respective channel unit to uniquely define one of said channels;   each of said transmitters comprising means multiplexing Y data buses from the associated switching unit for serial transmission over said transmission medium; and   each of said switching units further including a transmit portion having a channel strobe and data bus distributor pair for each of the associated channel units, said pair selectively distributing data from its respective channel unit into one channel time slot on one of Y data buses to the associated transmitter to uniquely define one of said channels into which said last mentioned data is inserted;   said east switching unit including means for selectively inserting signals in any one or more channels in said eastbound traffic passing therethrough from said eastbound receiver by substituting signals from any one or more of said east channel units for any one or more of said channels in said eastbound traffic;   said west switching unit including means for selectively inserting signals in any one or more channels in said westbound traffic passing therethrough from said westbound receiver by substituting signals from any one or more of said west channel units for any one or more of said channels in said westbound traffic,   whereby said west channel units receive signals from said west terminal and send signals to said west terminal, and said east channel units receive signals from said east terminal and send signals to said east terminal, said channel unit operators thus receiving and sending signals from and to the same terminal.   
     
     
       11. The invention according to claim 10 wherein said west switching unit comprises user controlled drop and insert channel selector means for dropping any channel in said eastbound traffic to any said west channel unit and for inserting signals from any said west channel unit into any channel in said westbound traffic, and wherein said east switching unit comprises user controlled drop and insert channel selector means for dropping any channel in said westbound traffic to any said east channel unit and for inserting signals from any said east channel unit into any channel in said eastbound traffic.   
     
     
       12. A bidirectional drop and insert channel bank for receiving signals from either or both of a pair of end terminals by dropping one or more channels from a transmission medium therebetween, and for sending signals to either or both of said terminals by inserting one or more channels on said transmission medium, said terminals being assignable a designation as a west terminal and an east terminal, and said transmission medium thereby having an eastbound portion and a westbound portion, comprising: a pair of receivers comprising an eastbound receiver connected to said eastbound portion of the transmission medium for receiving signals from the west terminal, and a westbound receiver connected to the westbound portion of the transmission medium for receiving signals from the east terminal;   a pair of transmitters comprising a westbound transmitter connected to the westbound portion of the transmission medium for sending signals to the west terminal, and an eastbound transmitter connected to the eastbound portion of the transmission medium for sending signals to the east terminal;   a pair of switching units comprising an eastbound switching unit and a westbound switching unit;   a pair of groups of one or more channel units, comprising an eastbound group of one or more channel units connected to the eastbound switching unit, and a westbound group of one or more channel units connected to the westbound switching unit;   means for connecting each of the switching units between one of the receivers and transmitters so that eastbound signal traffic travels through said eastbound receiver then through said eastbound switching unit then through said eastbound transmitter, and   westbound signal traffic travels through said westbound receiver then through said westbound switching unit then through said westbound transmitter;     each of said receivers comprising means demultiplexing data from said transmission medium into a matrix of X channel strobes of Y data buses;   each of said switching units including a receive portion having a channel strobe and data bus selector pair for each of the associated channel units, said pair delivering a single channel strobe and single data bus to its respective channel unit to uniquely define one of said channels;   each of said transmitters comprising means multiplexing Y data buses from the associated switching unit for serial transmission over said transmission medium; and   each of said switching units further including a transmit portion having a channel strobe and data bus distributor pair for each of the associated channel units, said pair selectively distributing data from its respective channel unit into one channel time slot on one of Y data buses to the associated transmitter to uniquely define one of said channels into which said last mentioned data is inserted;   said eastbound switching unit including means for selectively dropping any one or more channels in said eastbound traffic passing therethrough from said eastbound receiver to any one or more of said eastbound channel units;   said eastbound switching unit includes means for selectively inserting signals in any one or more channels in said eastbound traffic passing therethrough from said eastbound receiver by substituting signals from any one or more of said eastbound channel units for any one or more of said channels in said eastbound traffic;   said westbound switching unit including means for selectively dropping any one or more channels in said westbound traffic passing therethrough from said westbound receiver to any one or more of said westbound channel units; and   said westbound switching unit including means for selectively inserting signals in any one or more channels in said westbound traffic passing therethrough from said westbound receiver by substituting signals from any one or more of said westbound channel units for any one or more of said channels in said westbound traffic,   whereby said eastbound channel units receive signals from said west terminal and send signals to said east terminal, and said eastbound channel units receive signals from said east terminal and send signals to said west terminal, channel unit operators receiving and sending signals from and to opposite terminals.   
     
     
       13. An inserting channel bank for a transmission system carrying a plurality of multiplexed digital channels on a transmission medium between a pair of terminals, comprising: receiver means connected to said transmission medium for receiving said channels;   switching means connected to said receiver means for selecting one or more of said channels;   a plurality of channel units connected to said switching means;   transmit means, connected to provide data from said switching means to said transmission medium, for inserting on the latter one or more channels from selected one or more of said channel units, respectively;   means for providing from said receiver means one or more synchronization signals and a clock signal, said clock signal being provided to said switching means and to said transmit means; and   delay means responsive to said one or more synchronization signals and to said clock signal for providing a delayed synchronization signal to said transmit means so that said inserting by the latter is aligned with said data from said switching means, whereby the alignment avoids a requirement of buffering said data.   
     
     
       14. The channel bank of claim 13, wherein said one or more synchronization signals comprise a frame sync and multiframe sync, wherein said clock is an edge aligned clock and said delayed synchronization signal is a delayed multiframe sync. 
     
     
       15. A drop and insert channel bank for a digital transmission system carrying a plurality of multiplexed channels on a transmission medium between a pair of terminals, comprising: a receive unit connected to said transmission medium for receiving said channels;   a transmit unit connected to said transmission medium for transmitting said channels;   a data switching unit connected between said receive unit and said transmit unit for selectively dropping any one or more channels through said receive unit and inserting any one or more channels through said transmit unit; and   a plurality of channel units each corresponding to an individual channel connected to and sharing in common said data switching unit, each channel unit selectable to carry data from or to any of said channels in said transmission medium through said commonly shared data switching unit, whereby to enable any of said channels on said transmission medium to be dropped or inserted without fully equipping said channel bank with dedicated equipment for every said channel;   means for providing from said receive unit one or more synchronization signals and a clock signal, said clock signal being provided to said data switching unit and to said transmit unit; and   delay means responsive to said one or more synchronization signals and to said clock signal for providing a delayed synchronization signal to said transmit unit so that said inserting through said transmit unit is aligned with data received at the transmit unit from the data switching unit, whereby the alignment avoids a requirement of buffering said data.   
     
     
       16. The invention according to claim 3, wherein the output of said channel strobe distributors of the slave data switching unit is connected to said inhibit controller of the master data switching unit to provide an inhibit command thereto such that the correspondent output through-traffic channel from said insert selector of the master data switching unit is blocked by its said inhibit gate and the insert channel from said insert selector of the slave data switching unit is passed through its said inhibit gate to said transmit unit.